1. Field of the Invention
The present invention is generally related to the wireless distribution of high-quality audio signals and, in particular to a system and methods of distributing high-bitrate, multichannel, audio wirelessly while maintaining a constant, low, playback to source latency and channel to channel phase coherency.
2. Description of the Related Art
In the audio space there are many places that latency, high quality, and more than two channels are critical to the quality of the experience. It is also difficult to retrofit standard spaces with cables to the support multiple channels of audio. Today's definition of high end audio in the Home Theater space is 7 channels of audio samples at 48,000 samples per second with 24 bits of data per sample. Further, the marketplace is rapidly maturing from 5.1 (6 channel) to 11.1 (12 channel) sound system requirements.
Conventional wireless solutions rely on simple, low-cost radio technologies, such as frequency modulation (FM) and basic spread spectrum modulation schemes. The consequence of this is a reduction in the number of bits used for each audio sample, with a corresponding reduction in dynamic range and audio quality.
A critical requirement exists in both spaces to minimize and establish a constant or fixed latency in the system and to keep all channels aligned in time. Latency refers to time delays measured from audio source-to-output and from channel-to-channel. Source-to-output delays are a problem for all sound venues including, in particular, Home Theater and other video/audio systems, where the audio program material is synchronized to a video screen (“lip-sync”). Acoustics engineers generally consider source-to-output delays greater than 10 milliseconds to be noticeable. As for latency from channel-to-channel, the human ear is extremely sensitive to these phase delays and experts describe audio delivered with channel-to-channel delays greater than 1 millisecond as sounding “disjointed” or “blurry”.
The same data and sampling rate are in use in recording and sound reinforcement, only the desired number of channels is generally between 8 and 32. In conferencing use, the latency and wireless requirement are compounded by a need for accurate routing of audio paths with intelligent addition of signals and echo cancellation.
Consequently, there is a clear need to solve all of these problems in a wireless audio distribution system.